regex: new options returning interface to the regex module (#6062)

vlib/regex/regex_opt.v

@@ -0,0 +1,34 @@
+module regex
+import strings
+
+// compile_opt compile RE pattern string
+pub fn (mut re RE) compile_opt(pattern string) ? {
+	re_err,err_pos := re.impl_compile(pattern)
+	
+	if re_err != compile_ok {
+		mut err_msg := strings.new_builder(300)
+		err_msg.write("query: $pattern\n")
+		line := "-".repeat(err_pos)
+		err_msg.write("err  : ${line}^\n")
+		err_str := re.get_parse_error_string(re_err)
+		err_msg.write("ERROR: $err_str\n")
+		return error_with_code(err_msg.str(), re_err)
+	}
+}
+
+// new_regex create a RE of small size, usually sufficient for ordinary use
+pub fn new() RE {
+	return impl_new_regex_by_size(1)
+}
+
+// new_regex_by_size create a RE of large size, mult specify the scale factor of the memory that will be allocated
+pub fn new_by_size(mult int) RE {
+	return impl_new_regex_by_size(mult)
+}
+
+// regex_opt create new RE object from RE pattern string
+pub fn regex_opt(pattern string) ?RE {
+	mut re := new()
+	re.compile_opt(pattern)?
+	return re
+}